Mycophenolate mofetil as an alternate immunosuppressor for autoimmune lymphoproliferative syndrome

Understanding the Spectrum of Immune Dysregulation Manifestations in Autoimmune Lymphoproliferative Syndrome and Autoimmune Lymphoproliferative Syndrome-like Disorders

As a disorder of immune dysregulation, autoimmune lymphoproliferative syndrome (ALPS) stems from pathogenic variants in the first apoptosis signal-mediated apoptosis (Fas) and Fas-ligand pathway that result in elevations of CD3+ TCRαβ+ CD4- CD8- T cells along with chronic lymphoproliferation, a heightened risk for malignancy, and importantly for the rheumatologist, increased risk of autoimmunity. While immune cytopenias are the most encountered autoimmune phenomena, there is increasing appreciation for ocular, musculoskeletal, pulmonary and renal inflammatory manifestations similar to more common rheumatology diseases. Additionally, ALPS-like conditions that share similar clinical features and opportunities for targeted therapy are increasingly recognized via genetic testing, highlighting the need for rheumatologists to be facile in the recognition and diagnosis of this spectrum of disorders. This review will focus on clinical and laboratory features of both ALPS and ALPS-like disorders with the intent to provide a framework for rheumatologists to understand the pathophysiologic drivers and discriminate between diagnoses.

Autoimmune lymphoproliferative syndrome: A disorder of immune dysregulation

Autoimmune Lymphoproliferative Syndrome (ALPS) is an autoimmune disease that has been reported in over 2200 patients. It is a rare, genetic disease where pathogenic variants occur in the extrinsic pathway of apoptosis. Various mutations in different genes, such as FAS, FASL, and CASP10, can result in ALPS. Most commonly, pathogenic variants occur in the FAS receptor. This malfunctioning pathway allows for the abnormal accumulation of lymphocytes, namely CD3 + TCRαβ+CD4 - CD8- (double negative (DN) T) cells, which are a hallmark of the disease. This disease usually presents in childhood with lymphadenopathy and splenomegaly as a result of lymphoproliferation. Over time, these patients may develop cytopenias or lymphomas because of irregularities in the immune system. Current treatments include glucocorticoids, mycophenolate mofetil, sirolimus, immunoglobulin G, and rituximab. These medications serve to manage the symptoms and there are no standardized recommendations for the management of ALPS. The only curative therapy is a bone marrow transplant, but this is rarely done because of the complications. This review serves to broaden the understanding of ALPS by discussing the mechanism of immune dysregulation, how the symptoms manifest, and the mechanisms of treatment. Additionally, we discuss the epidemiology, comorbidities, and medications relating to ALPS patients across the United States using data from Cosmos.

Double-negative T cells in autoimmune diseases

PURPOSE OF REVIEW

TCRαβ+CD4-CD8- double-negative T (DNT) cells, a principal subset of mature T lymphocytes, have been closely linked with autoimmune/inflammatory conditions. However, controversy persists regarding their ontogeny and function. Here, we present an overview on DNT cells in different autoimmune diseases to advance a deeper understanding of the contribution of this population to disease pathogenesis.

RECENT FINDINGS

DNT cells have been characterized in various chronic inflammatory diseases and they have been proposed to display pathogenic or regulatory function. The tissue location of DNT cells and the effector cytokines they produce bespeak to their active involvement in chronic inflammatory diseases.

SUMMARY

By producing various cytokines, expanded DNT cells in inflamed tissues contribute to the pathogenesis of a variety of autoimmune inflammatory diseases. However, it is unclear whether this population represents a stable lineage consisting of different subsets similar to CD4+ T helper cell subset. Better understanding of the possible heterogeneity and plasticity of DNT cells is needed to reveal interventional therapeutic opportunities.

Autoimmune Lymphoproliferative Syndrome: An Overview

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited nonmalignant lymphoproliferative disorder characterized by heterozygous mutations within the first apoptosis signal receptor (FAS) signaling pathway. Defects in FAS-mediated apoptosis cause an expansion and accumulation of autoreactive CD4- and CD8- (double-negative) T cells, leading to cytopenias, splenomegaly, lymphadenopathy, autoimmune disorders, and a greatly increased lifetime risk of lymphoma. The differential diagnosis of ALPS includes infection, other inherited immunodeficiency disorders, primary and secondary autoimmune syndromes, and lymphoma. The most consistent pathologic feature is a florid paracortical expansion of double-negative T cells in lymph nodes. A presumptive clinical diagnosis can be made from symptoms and a constellation of laboratory test results. However, a definitive diagnosis requires ancillary testing and enables disease subclassification. Recognition of ALPS is critical, as treatment with immunosuppressive therapies can effectively reduce or ameliorate symptoms for most patients.

[Advances in the knowledge and management of autoimmune lymphoproliferative syndrome]

Autoimmune lymphoproliferative syndrome (ALPS) represents a failure of apoptotic mechanisms to maintain lymphocyte homeostasis. ALPS often manifest in childhood with cytopenias, chronic non-malignant lymphoproliferation and autoimmune complications. A number of new insights have improved the understanding of the genetics and biology of ALPS. The treatment of the disease has changed and mycophenolate mofetil and sirolimus have been demonstrated to have marked activity against the disease, improving quality of life for many patients. These will be discussed in this review.

Monogenic defects in lymphocyte apoptosis

PURPOSE OF REVIEW

The recognition that apoptosis - programmed cell death - is an important mechanism in immune homeostasis has led to the identification of human disorders associated with defects in the critical control mechanism.

RECENT FINDINGS

Patients have been identified with defects affecting the extrinsic apoptotic pathway mediated by the protein receptor FAS which results in the autoimmune lymphoproliferative syndrome and more recently in defects affecting the intrinsic apoptotic pathway mediated by RAS proteins resulting in the RAS-associated autoimmune leukoproliferative disorder. This review summarizes the immunopathogenesis, clinical features and diagnostic approaches to these human disorders.

SUMMARY

Apoptotic pathways are critical in the maintenance of leukocyte homeostasis, and genetic defects impacting these can result in clinical disease manifested as expansion of selected leukocyte populations, autoimmunity, increased risk for malignancy and in some situations defects in host defense.

[Primary immunodeficiencies presenting with autoimmune cytopenias in adults]

Although primary immunodeficiencies (PID) are typically marked by increased susceptibility to infections, autoimmune manifestations have increasingly been recognized as an important component of several forms of PID. Here, we discuss two forms of PID in which autoimmune cytopenias are particularly common and may be the first manifestation of the disease in adults: autoimmune lymphoproliferative syndrome (ALPS) and common variable immunodeficiency (CVID). Approximately one fifth of patients with CVID develop autoimmune diseases, and immune thrombocytopenic purpura (ITP) and autoimmune hemolytic anemia (AHA) are the most common. Since autoimmune cytopenias frequently precede the diagnosis of CVID, testing for immunoglobulin levels should be performed in patients diagnosed with AITP and AHA. Patients with CVID in association with autoimmune cytopenias have a "particular phenotype" with lower susceptibility to infection and higher susceptibility to autoimmune manifestations and, for patients with AHA, a more frequent development of splenomegaly and lymphoma. Corticosteroids and high doses of intravenous immunoglobulins (IVIg) seem to have the same efficacy as in idiopathic AITP and AHA. Splenectomy and rituximab are as effective as in idiopathic autoimmune cytopenias but are associated with an increased risk of severe infection and should, in our opinion, be considered only for those rare patients with "refractory diseases". The course and outcome of autoimmune cytopenias is not affected by supportive IVIg therapy. Autoimmune destruction of blood cells affects over 70% of ALPS patients. The median age of first presentation is 24 months of age, but with increasing awareness of this condition, adults with autoimmune cytopenias are now being diagnosed more frequently. Testing for ALPS should therefore be considered in young adults with unexplained Evan's syndrome. Patients usually respond to immunosuppressive medications, including corticosteroids. Unlike many patients with idiopathic autoimmune cytopenias, the cytopenias in patients with ALPS typically do not respond to IVIg. After corticosteroids, the immunosuppressive drug that is the most studied in ALPS patients is mycophenolate mofetyl. Rituximab and splenectomy are relatively contraindicated in ALPS because of an increase risk of severe infection and should be reserved for patients who fail all other therapies.

New advances in the diagnosis and treatment of autoimmune lymphoproliferative syndrome

PURPOSE OF REVIEW

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of disrupted lymphocyte homeostasis, resulting from mutations in the Fas apoptotic pathway. Clinical manifestations include lymphadenopathy, splenomegaly, and autoimmune cytopenias. A number of new insights have improved the understanding of the genetics and biology of ALPS. These will be discussed in this review.

RECENT FINDINGS

A number of key observations have been made recently that better define the pathophysiology of ALPS, including the characterization of somatic FAS variant ALPS, the identification of haploinsufficiency as a mechanism of decreased Fas expression, and the description of multiple genetic hits in FAS in some families that may explain the variable penetrance of the disease. In addition, ALPS has been shown to be a more common condition, as patients diagnosed with other disorders, including Evans syndrome and common variable immune deficiency, have been found to have ALPS. Finally, the treatment of the disease has changed as splenectomy and rituximab have been shown to have unexpected ALPS-specific toxicities, and mycophenolate mofetil and sirolimus have been demonstrated to have marked activity against the disease.

SUMMARY

On the basis of novel advances, the diagnostic algorithm and recommended treatment for ALPS have changed significantly, improving quality of life for many patients.

Pentostatin for treatment of refractory autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS), a disorder of programmed cell death, could be due to a congenital defect in the Fas signaling pathway or other pathways for apoptosis. Most cases present with lymphoproliferation and certain autoimmune features such as thrombocytopenia, neutropenia, and anemia are due to excessive production of antibodies by B lymphocytes. Majority of cases present within the first few years of life. We report a case of ALPS presenting at birth which was refractory to splenectomy and immunosuppressive therapy, but responded to pentostatin followed by hematopoietic stem cell transplantation (HSCT).

Splenectomy in two children with autoimmune lymphoproliferative syndrome and massive splenomegaly

Treatment of patients with ALPS has varied but presently there is no consensus about the optimal therapy. Splenectomy is an option but data regarding the postsplenectomy outcome in pediatric ALPS patients remain very limited. We present two children who suffered from anemia and physical discomfort from the large spleen. Both patients underwent uneventful splenectomy and experienced significant improvement in cytopenia, daily activity and well-being. Furthermore the youngest patient showed a significant catch-up growth. We conclude that in selected patients with marked splenomegaly and ALPS, splenectomy may be considered a treatment option.

Rapid regression of lymphadenopathy upon rapamycin treatment in a child with autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is a genetic disorder of the immune system caused by inadequate induction of apoptosis via the Fas pathway, mainly characterized by generalized lymphadenopathy, splenomegaly, and autoimmune cytopenias, as well as increased risk of lymphoma. Although the clinical course of ALPS is highly variable, without treatment long-term prognosis is unsatisfactory for most patients. ALPS has been treated with most of the existing immunosuppressive agents, with variable success. We hereby present a case of a child with ALPS whose greatly enlarged lymph nodes rapidly regressed upon initiation of rapamycin, a novel potential therapeutic agent in the treatment of ALPS.

Advances in the management and understanding of autoimmune lymphoproliferative syndrome (ALPS)

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of T cell dysregulation caused by defective Fas-mediated apoptosis. Patients with ALPS can develop a myriad of clinical manifestations including lymphadenopathy, hepatosplenomegaly, autoimmunity and increased rates of malignancy. ALPS may be more common that originally thought, and testing for ALPS should be considered in patients with unexplained lymphadenopathy, hepatosplenomegaly, and/or autoimmunity. As the pathophysiology of ALPS is better characterized, a number of targeted therapies are in preclinical development and clinical trials with promising early results. This review describes the clinical and laboratory manifestations found in ALPS patients, as well as the molecular basis for the disease and new advances in treatment.

Use of rituximab for refractory cytopenias associated with autoimmune lymphoproliferative syndrome (ALPS)

BACKGROUND

ALPS is a disorder of apoptosis resulting in accumulation of autoreactive lymphocytes, leading to marked lymphadenopathy, hepatosplenomegaly, and multilineage cytopenias due to splenic sequestration and/or autoimmune destruction often presenting in childhood. We summarize our experience of rituximab use during the last 8 years in 12 patients, 9 children, and 3 adults, out of 259 individuals with ALPS, belonging to 166 families currently enrolled in studies at the National Institutes of Health.

METHODS

Refractory immune thrombocytopenia (platelet count <20,000) in nine patients and autoimmune hemolytic anemia (AIHA) in three patients led to treatment with rituximab. Among them, seven patients had undergone prior surgical splenectomy; three had significant splenomegaly; and two had no palpable spleen.

RESULTS

In seven out of nine patients with ALPS and thrombocytopenia, rituximab therapy led to median response duration of 21 months (range 14-36 months). In contrast, none of the three children treated with rituximab for AIHA responded. Noted toxicities included profound and prolonged hypogammaglobulinemia in three patients requiring replacement IVIG, total absence of antibody response to polysaccharide vaccines lasting up to 4 years after rituximab infusions in one patient and prolonged neutropenia in one patient.

CONCLUSION

Toxicities including hypogammaglobulinemia and neutropenia constitute an additional infection risk burden, especially in asplenic individuals, and may warrant avoidance of rituximab until other immunosuppressive medication options are exhausted. Long-term follow-up of ALPS patients with cytopenias after any treatment is necessary to determine relative risks and benefits.

Genetic defects of apoptosis and primary immunodeficiency

Programmed cell death is important for maintaining lymphocyte homeostasis. Several human-inherited diseases with impaired apoptosis have been identified at the genetic level: autoimmune lymphoproliferative syndrome, caspase-8 deficiency state, and X-linked lymphoproliferative syndrome. These diseases feature excess lymphocyte accumulation, autoimmunity, or immunodeficiency. Elucidating their molecular pathogenesis has also provided new insights into the signaling mechanisms regulating apoptosis and lymphocyte activation.